1. Field of the Invention
This invention relates to a copper foil having a glossy surface with excellent oxidation resistance and also to a method of manufacturing the same and, more particularly, relates to a copper foil for printed wiring having excellent oxidation resistance characterized by a composite layer containing chromium, zinc, phosphorus, and nickel formed on the glossy copper foil surface and also to a method of manufacturing the same.
2. Prior Art
Copper foils that have hitherto been used for printed wiring purposes are those whose glossy surfaces are chromated or otherwise treated, as by chelation with copper using an organic agent such as benzotriazole, for enhanced corrosion resistance.
Those treated copper foils are improved in corrosion resistance as well as oxidation-tarnishing resistance during the course of lamination to insulation substrates. Nevertheless, they are unsatisfactory in other properties such as solder wettability and oxidation resistance at the time of heating.
Under the circumstances Japanese Patent Application Kokai No. 5-299834 discloses an electrolytic copper foil characterized by a composite layer containing chromium, zinc, and phosphorus formed on the glossy surface of the foil. Advantages claimed of the foil are good resistance to heating and oxidation tarnishing during and after lamination to insulation substrates, corrosion resistance, solder wettability, and ease of black oxidation treatment.
However, the copper foil provided with a composite layer containing chromium, zinc, and phosphorus as taught in the Patent Application Kokai No. 5-299834 has an oxidation resistance problem. It has been observed to undergo serious oxidation tarnishing of the entire surface under certain heating conditions (e.g., at 180.degree. C. for 30 minutes).